______,Dust with flour and brown in 1 tablespoon of margarine.,In another skillet, melt 2 tablespoons margarine and saute mushrooms and onion until tender. Add mushroom and onion mixture to beef.,Add bouillon and stir well to form a paste.,Add tomato paste, sherry and mustard. Simmer over lowest heat, covered, for 30 minutes.,Five minutes before serving, add sour cream. Spoon meat mixture over the egg noodles.,Cook noodles by bag directions and add poppy seed. Serves 4.